1. Field of the Invention
The present invention relates to a method for focusing at least a deflected light beam of a light beam polarized or modulated by an acoustooptical element onto an optical information recording medium or an optical disk to form prewobble pit, concentric prepit or concentric pregroove, and optical apparatus for the optical information recording medium.
2. Discussion of the Related Art
In an optical disk having prepits representing an ID signal such as an address formed for each sector to permit recording of data to a desired sector, it has been known to form wobbling pits when prepits are formed and tracking of a laser beam is controlled by using the wobbling pits when data is recorded on or reproduced from an optical disk.
However, the sizes of the wobbling pits are different from each other and accurate tracking control is not attained.
When concentric pregrooves are formed on an optical disk as an optical recording medium, a start point and an end point of the pregroove do not coincide and it is difficult to quickly form continuous concentric pregrooves.
FIG. 18 shows a perspective view of an example of an optical disk exposure apparatus. An acoustooptical element 7 is arranged in an optical path extending from a light source 6 objective lens 11.
The acoustooptical element 7, functions to control a light intensity and reduce noise ("Summary of Optical Disk Processing Technique" by Y. Okino, Nihon Kogyo Technical Center, May 15, 1985)